The present invention relates to net wrapping devices for large round balers and more specifically relates to arms for applying pressure to such rolls so as to resist the pulling off of net from the roll during the wrapping process and thereby tension the wrap material. U.S. Pat. No. 5,974,764 issued Nov. 2, 1999 to Anstey et al. discloses a large round baler net wrapping apparatus including a gas cylinder arranged for applying a force to a pressure arm including a pressure roll engaging a supply roll of surface wrap material in order to hold it tightly against one of a pair of wrap material feed rolls operable for feeding wrap material for delivery to the baling chamber of a large round baler for wrapping a bale located there. This application further discloses a small idler roll mounted close to the one feed roll in order to increase the surface area of the feed roll in contact with the net so that the pull exerted on the net by a bale being wrapped would not induce excessive slippage of the net and thereby aid in stretching the net the amount desired for tight wrapping.
However, the small idler roll has the disadvantage that, during the loading of a new roll of wrap material for being dispensed by the wrapping mechanism, it is somewhat difficult for one person to thread the free end the new roll of wrap material about the idler roll and then into the nip of the feed rolls. While the total amount of resistance to unrolling can be increased by having the pressure arm disposed for forcing the wrap material roll against the front wall of the housing containing the roll of wrap material, this action is not desirable since it is difficult to control the resistance due to changing moisture and other environmental conditions. Furthermore, although the geometrical relationship between the known pressure arm and the wrap material roll can be designed to increase the pressure exerted by the roll of material on the upper feed roll to an extent which would make it possible to eliminate the small idler roll, this arrangement is not entirely satisfactory since it results in the pressure roller being located in an upper zone of the wrap material. Then, because of various factors including dust, belt tolerances, pulley surfaces, etc, one can expect an occasional abrupt start of the v-belt drive of the upper net feed roll which can cause the roll of net material to shift rearward, out of position for proper feeding. While one solution would be to move the pressure roll to engage a more rearward zone of the supply roll, this would increase the frictional engagement of the supply roll with the front wall of the wrapping mechanism while decreasing the force pressing the supply roll against the feed roll, both changes being undesirable as it makes the control of net stretch less precise.